El Niño events recorded by redox sensitive trace elements in sedimentary records from Genovesa Lake, Galápagos

Redox-sensitive trace elements (RSTE) are well-established proxy indicators of the geochemical conditions on Earth. They have proven useful for revealing early Earth's oxygenation and detailing past anoxic episodes in aquatic systems. Here we present evidence that large-scale Tropical Pacific climate variability associated with El Niño-Southern Oscillation (ENSO) influences the partitioning of solid, dissolved, and particulate phases of manganese, iron, and molybdenum in a meromictic, hypersaline lake of the Galápagos archipelago. The concentration of these RSTE as a geochemical proxy in this system reveals the timing of ENSO events between the years 1985-2016 CE. Additionally, these geochemical signals are associated with blooms in primary productivity, which is highly influenced by local rainfall events. Thus, we find strong evidence that climatic events influence the geochemical profile of this aquatic system and deposited sediments, such that levels of RSTE are elevated far above background levels during wet, productive El Niño years. As a result of this on/off signal behavior, RSTE offer great promise for reconstructing individual El Niño events throughout the Holocene in this lake sediment archive. Ideally, this approach could also be applied to other El Niño regions to better reconstruct past climate when combined with traditional paleoclimate proxies.